Help needed understanding a MOSFET chart

Discussion in 'General Electronics Chat' started by Xelectro, Aug 13, 2012.

  1. Xelectro

    Thread Starter New Member

    Aug 12, 2012
    I am currently experimenting with a power MOSFET IRF510
    And I am trying to understand how to properly read the output characteristic chart, to determine required Vth to bias the MOSFET drain at half rail voltage (class A amp).
    Vcc 12v
    Rload 24R
    Id (max) 500ma
    Desired id at bussing 250ma
    Need help understanding the chart.
  2. crutschow


    Mar 14, 2008
    Because of the large unit-to-unit variation of Vth you can't use that by itself to bias the transistor at 1/2 the supply voltage. Thus a resistor is typically added between the transistor source and ground to swamp out the Vth variations and give a more stable bias point. Since this resistor also reduces the transistor gain you can bypass it with a capacitor to increase the gain for AC signals. Here is a discussion of biasing.